Initial setup: mac_os installer with custom config

Contains both components needed for Mac setup:
- mac_os/: Installer scripts (from bkuhlmann/mac_os)
- mac_os-config/: Custom app configuration

Configured apps:
- Homebrew formulas: atuin, bash, ffmpeg, mas, mole, node, rename, ykman
- Homebrew casks: chromium, deepl, element, nextcloud, nova, proton suite, signal, transmit
- App Store: Affinity suite, Bitwarden, Final Cut Pro, Invoice Ninja, iWork, PastePal, xSearch

Usage: cd mac_os && ./bin/run

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mac_os-config/bin/install_shell

@@ -0,0 +1,11 @@
+#! /usr/bin/env bash
+
+# Installs shell.
+
+if [[ -z $(cat /etc/shells | grep "$(get_homebrew_bin_root)/bash") ]]; then
+  sudo bash -c "printf '$(get_homebrew_bin_root)/bash\n' >> /etc/shells"
+  chsh -s "$(get_homebrew_bin_root)/bash"
+  rm -f "$HOME/.bash_profile"
+else
+  printf "%s\n" "Shell is installed."
+fi